There is a class of tumors called "hormone-dependent" tumors, which generally occur in the target organs of hormones, and their growth can be promoted by or dependent on the presence of those hormones. For example, the growth of some mammary cancers is promoted by estrogen, the growth of some prostate cancers is promoted by androgen, and the growth of some thyroid cancers is promoted by thyroid stimulating hormone (TSH). Hormonal endocrine therapies are widely used for the treatment of such hormone-dependent tumors. For example, excision of estrogen-producing ovaries has been employed as an endocrine therapy for some estrogen-dependent mammary cancers. In addition, a widely used treatment for mammary cancer is the administration of an anti-estrogenic agent such as tamoxifen, which competes with estrogen for binding to the estrogen receptor, thereby exerting an antitumor effect. A biopsy of a mammary cancer is generally examined for the presence or absence of estrogen receptors in the cancerous tissue, in order to determine whether administration of an anti-estrogenic agent is indicated. In practice, a correlation between the presence of estrogen receptors and the clinical effectiveness of the anti-estrogenic agent is clinically significant. However, a positive estrogen receptor test can be misleading if the estrogen receptor is physiologically and functionally inactive. Tumors having estrogen receptors therefore do not necessarily exhibit estrogen-dependent proliferation.
Recent studies show that some tumors and other diseased tissues are capable of producing hormones which cause them to proliferate or cause the diseased tissue to be further aggravated. For example, some mammary cancers produce an enzyme called aromatase which converts androgens, such as testosterone, into estrogen. High estrogen levels in such cancer tissues have been reported. Uchimi et al., 90 J. JPN. SURG. SOC. 920-927(1989). An effective treatment for a tumor having aromatase activity and exhibiting estrogen-dependent proliferation is to administer an aromatase inhibitor. However, aromatase activity tests are rarely carried out on tumor tissue because of the difficulty in sampling the diseased tissue and in obtaining an adequate amount of tissue for determining enzymatic activity. Tumors are therefore usually only screened for the presence of estrogen receptors as an indication for aromatase inhibitor therapy. However, this test does not confirm the presence of aromatase activity, and may result in misdiagnosis because not all tumors having estrogen receptors exhibit aromatase activity, nor do all tumors having estrogen receptors necessarily exhibit estrogen-dependent proliferation. These problems are not only encountered in estrogen-related cancers, but also in other hormone-dependent cancers and diseases, and may involve one or more hormones.